Production of monochlorisobutyric acid



Patented June 9, 1936 a v 2,043,010 w PRODUCTION or mgggcmomsonomro Donald J. Loder, Wilmington, and Emil D. Ries,

Gordon Heights, Del., assignors to E. I. duPont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application February 21, 1934,

Serial No. 712,354

12 Claims. (Cl. 260113) This invention relates to the manufacture of Of other chlorinating catalyst as hereinbefore dechlorisobutyric acid and more particularly to a fined. While it has been found that a small method for the production of monochlorisobutyric amount, even a fraction of a per cent., will accelacid from isobutyric acid and chlorine. erate the desired chlorination and whereas, if

a An object of the present invention is to provide e m u ts up to end including y W ht 5 an improved process for making monochlorisomay be employed, the amount of sulfur should butyric acid in high yield and with a minimum not exceed that figure, for with a larger proporamount of higher chlorinated bodies and other tion we have found that undesirable quantities by-products, of polychlorisobutyric acid and products of side it) It is a further object of the invention to provide reactions are obtained. The chlorination, which 0 methods of procedure and operating conditions s exothermic,-may be initiated and carried on whereby, as desired, preponderating proportions at ordinary temperatures, especially under the of alphamonochlorisobutyric acid or betamonoinfluence of light, as well as at various temperchlorisobutyric acid may be obtained. atures up to and including about 135 C. How- Other objects and advantages .of the invention ever, g ne ally speaking, i s been found D 15 will be apparent as it is better understood from ble to main ain the r ac on mi tu e, y Suitthe following specification and examples setting able C o i g. t a temperature Within t range forth its preferred embodiments. of about 125 to 130 (3.

According to the invention, monochlorisobuty- It is to be understood that while, as hereinafter ric acid is obtained in good yield and with a minexplained, the yield of monochlor acid may also 20 imum amount of higher chlorinated products and be favorably influenced by the extent of chlorinaother by-products by conducting gaseous chlotion, for any given amount of chlorination mono rine into a body of isobutyric acid containing specchlor acid formation is favored by employing cataified amounts of dissolved chlorinating catalyst, lyst concentrations within the above stated limits.

as which latter may be isobutyryl chloride or isobu- W h ve f und hat. ap t from t f re in g5 tyric anhydride or a substance capable of reactobservation as to the importance of the concening, in the presence of chlorine and isobutyric tration of catalyst the extent to which monoacid, to form one or both of these. Substances chlorisobutyric acid is produced to the exclusion capable of so reacting include generally inorganic of other chlorinated bodies and by-products, is

'30 2' organic acid halides or anhydrides, such, for critically affected by the extent of the ehlorina- 3 example, as sulphur chloride (or sulphur, which tion. Generally speaking, however, neither the in the presence of chlorine forms sulphur chlorate at which chlorine is introduced, theelapsed ride), thionyl chloride, phosphorus chloride, sultime, nor the actual gain of weight is a reliable phur trioxide, phosphorus oxides, chlorides or ancriterion of the degree of monochlorisobutyric 85 hydrides of acetic, propionic, butyric, and benacid production. On the other hand, our investi- 5 zoic acids, etc. Substances of the classes named gations have shown that the relative yield of favor formation of isobutyryl chloride and/or monochlorisobutyric acid is directly connected anhydride in presence of chlorine and isobutyric with the concentration of unreacted isobutyric acid, hence catalyze chlorisobutyric acid formaacid in the reaction mixture. More specifically 40 tion which apparently proceeds thus: isobutyryl we have found that the maximum production of 40 chlorideisobutyric anhydridechlorisobutyric monochlorisobutyric acid is obtained when the acid. chlorination is carried to, and stopped at. sub- Of the catalysts referred to, sulfur best comstantially the point where isobutyric acid has bines efflcacy and cheapness and accordingly the completely disappeared from the reaction system.

invention is hereinafter described particularly In the practical application of this observation 45 with reference to the use of a sulfur catalyst, al to the production of monochlorisobutyric acid, though it is to be understood that the use of equivwe have found that the specific gravity of the realent amounts of the other chlorinating catalysts action mixture is the most reliable and practical is likewise within the scope of the invention. guide to the extent to which the desired chlorina In accordance with the invention, then, good tion has proceeded. That is to say, the specific 50 yields of monochlorisobutyric acid are obtained, operating conditions and apparatus having been with minimum amounts of higher chlorinated and selected and established in any particular case, other undesirable substances, by effecting the a trial chlorination run is made, in which, as the chlorination in the presence of dissolved sulfur reaction proceeds, samples are withdrawn and 65 not exceeding 4% by weight or equivalent amount examined for specific gravity and content of free isobutyric acid, the latter being determined, for example, by fractional distillation. Such tests having finally determined the specific gravity corresponding to the point at which the isobutyric acid has disappeared from the system, subsequent operation of the process is effected so that chlorination proceeds only up to the point at which this determined value of specific gravity is attained. While it is not necessary that this specific gravity be exactly duplicated in every case, we have found that the value cannot substantially be departed from without seriously afiecting the yield of monochlorisobutyric acid. As a matter of fact, variations of more than $0.01 from the specific gravity determined in the manner indicated, will, generally speaking, result in an undesirable decrease in the yield of monochlorisobutyric acid.

It will be noted that it is impossible to prescribe for all conditions of operation the optimum specific gravity to be attained. Thus variation in the nature and percentage of catalyst employed will necessarily alter the specific gravity of the reaction mixture. However, by way of illustration, in the chlorination of isobutyric acid containing 3% sulfur, maximum yield of monochlorisobutyric acid has been obtained by stopping the chlorination .when the, reaction mixture had attained a specific gravity of 1.185 to 1.190 at 30 C.

For many purposes there is a marked difference in the value of alphaand betachlorisobutyric acids, respectively. Accordingly, another feature of the invention is the provision of operating conditions whereby the production of either alpha-monochlorisobutyric or beta-monochiorisobutyric acid may be favored.

We have found that the relative proportions of alpha and betamonochlorisobutyric acid obtained are directly connected with the concentration of catalyst and also with the chlorination temperature. Specifically, we have discovered that the chlorination may be made to proceed so as to yield alphamonochlorisobutyric acid, practically to the exclusion of the betachlor acid, by effecting the chlorination at a temperature above about 115 C. and employing between 2 and 4% by weight of sulfur (or equivalent amount of other chlorinating catalyst) in the acid to be chlorinated. The best results have been obtained at a temperature of about 125-130 C. Operating under these general conditions, for example, we

-have been able to obtain a yield of 80% or more alphamonochlorisobutyric acid based on the isobutyric acid initially introduced, with substantially no betamonochlorisobutyric acid.

On the other hand, when it is desired to obtain principally betamonochlorisobutyric acid, we have found it most advantageous to operate with a sulfur content of from 0.3 to 2% (or equivalent amount of other chlorinating catalyst) and at a temperature of from room temperature to about 115', preferably at about 70 C. Operating under these conditions, we have been able to obtain a 60% yield of monochlorisobutyric acid, the ratio of betato alphachlor acid being as high as 4 to 1.

The following examples are given to illustrate in more detail the practical operation of the invention. It is to be understood, however, that the examples are illustrative only and that they may be varied widely, particularly as to specific proportions of materials, operating conditions, and. manipulative details, without departing from the invention.

Example 1.Alphachlorisobutyric acid is prepared in good yield as follows: A charge of 9 gallons of isobutyric acid is placed in a 50 liter Pyrex flask, surrounded by an oil bath heated with steam coils. A water-cooled glass condenser followed by an ice-cooled glass coil furnishes the desired reflux. Three per cent. by weight of sulfur is added to the charge. The temperature is raised to about 80 C. and a flow of sulfuric acidwashed chlorine is started. The temperature is 10 then raised to and maintained at 125-130 C. Vigorous stirring is used. Chlorination to the desired end point of a specific gravity of 1.1871.188 at 30 C. is completed after about six hours, 65 to 70 lbs. of chlorine having been run in. The product is practically entirely alphachlorisobutyric acid, with substantially no betachlor acid. On fractional distillation a yield of about 80% alphachlorisobutyric acid is obtained.

Example 2.-A mixture of alphaand betachlorisobutyric acids, with the latter preponderating,isprepared as follows: Chlorine was bubbled through a charge of 15.9 mols of isobutyric acid containing 0.35% dissolved sulfur. The temperature was maintained at 70 C. and the chlorlna tion interrupted when the specific gravity of the reaction mixture reached 1.208 0.). On fractional distillation, a yield of 60.4% of monochlorisobutyric acid was obtained, the ratio of alpha to betachlor acid therein being 0.241. 30

Example 3.Isobutyric acid (15.9 mols) was chlorinated in the presence of isobutyryl chloride (19%) as catalyst, the temperature being 130 and the chlorination being continued until the specific gravity of the material was 1.176 (30 0;). A yield of 79.2 monochlorisobutyric acid resulted, the ratio of alpha to betachlor acid being 6.6.

, Example 4.-By chlorinating isobutyric acid (12.75 mols) containing isobutyryl chloride (16.4%) as catalyst at 130 C. to a specific gravity of 1.139 (30 C.), a yield of 84% monochlorisobutyric acid was obtained, with a ratio of alpha to betachlor acid of 4.4.

Example 5.--When chlorinating isobutyric acid (11.35 mols) containing thionyl chloride (20.9%) as catalyst at 130 C., chlorination was discontinued when the specific gravity reached 1.134 (30 C.). The yield of monochlorisobutyric acid recovered was 83.5%, with a ratio of alpha to betachlor acid of 5.7.

Example 6.Using phosphorus trichloride (2%) as catalyst, isobutyric acid (15 gram mols)v was chlorinated at IOU-128 C. until the charge had gained 600 g. in weight, The yield of alpha monochlorisobutyric acid was 22%, of betamonochlorisobutyric acid 32%.

In the manufacture of monochlorisobutyric acid it is advisable to exclude iron from the reaction system since its presence accelerates formation of higher chlorinated bodies. Thus glasslined or enamel-lined equipment is recommended, or vessels made of corrosion resistant alloys that will not yield dissolved iron in the reaction system in question.

Various changes may be made in the invention, including modification of manipulative details and selection of catalyst equivalent to those specifically mentioned, without departing from the invention or sacrificing the advantages thereof.

We claim:

1. Process for the manufacture of monochlorisobutyric acid which comprises chlorinating isobutyric acid containing added sulfur in amount 4. Process for'the production of alphachlor-- isobutyric acid which comprises chiorinatingisobutyric acid in the presence of from 2 to 4% by weight of sulfur at a temperature within the range of 115 to 130 C.

5. Process for the production of alphachlorisobutyric acid which comprises chlorinating isobutyric acid in the presence of from 2 to 4% by weight of sulfurat a temperature within the range of 125-130 C.

6. Process for the production of betamonochlorlsobutyric acid which comprises chlorinating isobutyric acid in the presence of from 0.3 to-2% sulfur.

7. Process for the production of betamonochlorisobutyric acid which comprises chlorinating isobutyric acid in the presence of from. 0.3 to 2% sulfur at a temperature not in excess of C.

8. Process for the production of betamonochlorisobutyric acid which comprises chlorinating isobutyric acid in the presence of from 0.3 to 2% sulfur at a temperature of about 70 C.

between and C.

acid, the step which compriseschlorinating theisobutyric acid only until there is substantially no unchlorinated isobutyric acidpresent.

10. In a process for the manufacture of monochlorisobutyric acid in which isobutyric acid. is chlorinated in the presence of sulfur in an amount not in excess of 4% by weight of the isobutyrlc acid, the step which comprises chlorinating the isobutyric acid only until the specific gravity of the reaction mixture differs by not more than 0.01 from that just corresponding to complete disappearance of isobutyric acid.

11. Process for the manufacture of mcnochlorisobutyric acid. which comprises chlorinating isobutyric acid only until there is substantially no unchlorinated isobutyric acid present, the chicrination being eifected in the presence of from 2 to 4% by weight oi. sulphur.

12. Process for the manufacture of monochlorisobutyric acid which comprises chlorinating isobutyric acid only until the specific gravity of the reaction mixture differs by not more than 0.01 from that just corresponding to complete disappearance of the isobutyric acid, the chlorination being eflected in the presence of from 2 to 4% by weight of sulphur at a temperature ranging DONALD J. LODER. mm. D. RIES. 

